Photometric device



Jan. 15, 1952 H. KOTT PHOTOMETRIC DEVICE Filed Sept. 3, 1947 PatentedJan. 15, 1952 UNITED STATES PATENT. OFFICE 7 2,582,835 rnoronm'rmoDEVICE Hermann Kott, West Orange, N. J. Application September 3, 1947,Serial No. 771,973

(o1. ss23) 5 Claims. 1

This invention relates to photo-metric devices and has for its objectthe provision of such a device whichaccurately measures the totalquantity of lightradiation falling upon and illuminating an area orobject over an extendedtime periodand indicates periodically themeasurement of determined. quantities of such measured radiation.

Another object is to provide such a device which is .utilizable in thephotographic art as an exposure meter to control and regulate thedensity of the reduced silver salts in a film emulsion by exposure ofthe film to a measured quantity of radiation.

A further object is to provide an exposure meter photo-metric devicewhich measures light radiation in terms of quantity over an extendedtime interval and indicates periodically the measurement of adeterminedquantity of such radiation during said extended time interval.

Other objects will be apparent as the invention is more fullyhereinafter disclosed.

In accordance with these objects, I have devised a photo-metric devicewhich measures the total quantity of light radiation falling upon andilluminating an area or object over an extended time interval and whichindicatesv periodically during said time interval the measurement of adetermined quantity of said radiation. In the photographic art it ishighly desirable and of extreme importance that the density of radiationthe density of such reduced metal salts also depends primarily upon thequantity of such light radiation and variations in such quantity in adetermined time interval varies the density of the reduced metal saltsmaterially. It is therefore apparent that to obtain any desired densityin such reduced metal salts under conditions of varying light radiationintensity a measurement of the quantity of such radiation over anextended time interval with periodic indications of the measurement of adetermined quantity of such radiation enables the photographer to limitthe time of exposure of the film 2 to such radiation to determinedmultiples of the determined quantity or such radiation to obtain suchdetermined density.

The present invention is based upon the time interval required in aphoto-electric cell, having a light sensitive cathode and an anode indetermined spaced relation enclosed within an evacuated envelope for asufficient quantity of positive electrons to pass from the anode to thecathode, by the action of light radiation irradiating the photo-cell, toneutralize a determined charge of negative electrons on the cathodewhich is equal in voltage to a positive voltage impressed on the anode.I

By applying this same negative charge upon the grid element of athermionic device ofthe three electrode type, known in the art'as anelectro-meter tube, the negative charge may simultaneously be utilizedto prevent the flow of plate current in the said tube between thecathode and plate elements thereof until the negative charge has beenneutralized by the positive electron flow in the photo-cell. V I

The flow of plate current in the said e1ectro meter tube, uponneutralization of the said negative charge on the grid element thereof,then may be amplified sufliciently toactuate substan-- tiallyinstantaneously a relay switch device immediately recharging the, saidgrid electrode. of the electr c-meter tube and the said cathodeelectrode of the photo-cell with a negative ,charge haying av voltageapproximating that on the anode electrode of thephoto-cell, thusinterrupting the flow or plate current in the electro-meter tube andpreventing the flow of such plate current for another timetintervaluntil the flow of positive electrons in the photo-cell has againneutralized the negative charge on the photo-cell cathode. I v j I Asthe flow of positive electrons in the photocell is directly;proportional to the quantity of light radiation falling on thephoto-cell over an extended time interval, variations in the intensityof such radiation merely shortens or prolongs the time interval requiredfor the neutralization of a negative charge of any given voltage on thephoto-cell cathode which is equal but opposite to the positive voltageon the photo-cell anode.

Accordingly, by providing means actuated by the flow of the platecurrent in the said electrometer tube simultaneously with actuation ofthe relay switch means, adapted to indicate each occurrence of negativecharge neutralization, the total quantity of light radiationilluminating any given area or object may be determined .by the.

11 1 1 D is provided with nj p total number of suchtnegative chargeneutralizations, the radiation quantum of each neutralization being afunction of the negative charge voltage employed.

In the adaptation of this invention as a photometric device of theexposure meter type for use in the photographic art to control orregulate the time of exposure of a film negative to light radiationthereby to obtain a' desired density in the reduced metal salts in theemulsion on the film and a desired definition in the positive imagesreproduced therefrom, the precise quantum of light radiation pernegative charge neutraliza: tion normally is immaterial inasmuch as thetime of film exposure to the radiation usually includes or covers aplurality oi such neutralization time intervals. It is important,however, to so measure the radiation that the time or exposure islimited to the number of negative charge nsu ai e ls rather t a t .r eqeids. x o.- ure. where variations in n m intensity "eiist, asisnormallyth'e case. p H V In .this adaptation of the 'pre'sentinvention t e ph' i 'rc e e trqrm r u e 'a dre yf w t b amma. h reiabove iiislq e'q. i t w t il a' 'ec h fci ui fa i ap ra u el s n the, enen $.,t ih .,m a yo ra in unit are normally enclo's'ed within aradiation imrma l h s n ha i i an p we throu'gh in a position adapted todirect the radiation, which it is desired to measure, onto the phqt e ldi c osu m mbe he e i nterrupt the illumination of the photo-cell to inaate hea raws- Th rii ai dev m bsswfi ihihs el en r hi e ho s brine th ud cribs ous heajsa se ra at c able lil i ias may be d si e Without esseni d ur #9 3 e y'e a. .A 1 s e fic. e b d m il iq m he i n ive but n t aal m iai miih me; wi l ,jsq ib a 1 $i the. ran i e'ni wer found to bemost suitable s in a ii-hottia v e 9. he exiesu t fi 'i u n i nciw ede'ripi in st nb s a on w th t e aqb m anii df 'a g i in the sev al-ap r se m nts. a l i l circuit connecting the said elements are st-awn a rammatal vi The. Exp sur met r. f t is 1. .i u 'sja r n-swam .4 1 A .t asand. r a wit 8 WWW b tgenei sie wifliih a .mc'a ie mus n med at d il e?t, oueh which thefradiation tb bi i 31 A. BzpaP il lam I in the art and,per se, form no part of the}; sent inrenii a xcep i the. e r iwla .99 biii thereof and when feliectricallyiconnected and'enrgized ashereinafter'will be described. I g A indi a in he i wifi l i i a' i thephoto-cell li and the grid elementg of the 1 trb: gti e,.B a ele ric lbefifiid ili i i l b 1 l 9 1 i h Q i l 3 5 [is electrically coinie(;ied,v to one of the eentacts 1 e ,3 9 the lrelarsw ieh Cf Thpihr. 9 h ifia i a efl i a' bu' 's f tive potential "of determined wage and the an ea it e i e w fa s tbmec i a sourcelof positive potential ofsubstantially the same voltage.

he "lectro-rnagnetic'eoil "a' rghe ra' jswatt amplifier 'iiciiit inseries with the 'batiidde and cell A thereby interrupting the flow ofplate current in tube -B and the flow of current between anode andcathode in photo-cell A and de-energizing the coil 4 thus separatingcontacts 2 and 3. The flow of plate current in tube B stays interfasteduntil the negative charge on cathode c and grid 9 has again beenneutralized by irradiation of the cathode c.

Many different circuit arrangements are pos sible to accomplish theabove described desired remit. The circuit arrangement shown is onedesigned for operation from a single source of alternating eurretjttrtheusual 1 l 0 volt, 6 0 cycle type common throughout most power distribution systems. It comprises a transformer T the primary of which isenergized by 110 volt 6il cycle alternating current from power supplylines 10-40 in series with which are electrically connected safety fuseI I and switch means z rer energizing and de-energizing the transformerT.

Transformer T isprov'ided with a plurality of secondary windings Iromwhich current is drawn to energize separately; the cathode 5 ofelectrometer tube B; to provide a positive plate voltage of desiredconstant value onto the plate 6 of the said tubeB; to energize cathode13 of rectifier tube I4 and to provide a voltage output from therectified tube 14 off the proper valuefto' energize eoil 4 of relayswitch C and to providedi-rect current potentials, positive and negative'o'f equal value to apply to anode a and to cathode 'c and grid 9,respectively; in a 'c'arqatcew tn the above disclosure; also to providecurrent forener grzing an indicating device, such as a timer mecha- Itisbelieved that one sl illed inti e art will readily recognize and be'able to read the circuit diagram of the drawing without the necessityof detailedwritten description'ef the same. The essential departure fromprior art ia'cu e therein being that in the circuit the positive isidethereef is grounded instead "of the negative side. It is by thusgrounding the positive side, rather than the negative side of thecircuit, that ram able to impress on the cathode and grid 'elec} trodesof the photo-cell A and elec'tro meter tube B, respectively, thenegative charge re-- :quired fQr Qpe'ra tiOn of the photo-metric device,thenormal internal resistance of these devices preventing this negativecharge frcm passing through the devices to the'a'node and plateelements, respectively, for discharge to ground, until the internalresistance of the photo-cell A, by cathode irradiation, is loweredsufiiciently t'o permit negati harge neutralization, as hereinabovedescribed.

The essential element in the circuit is a source of direct current at asubstantially 'c'ons'tant v'oltage for application across the anodeandcathode of photo-cell A. "Ifhis is obtained through'a voltage regulatormeans of common type enclosed within dotted box lines 20. Relay switchesatclosed within dotted box lines '2! "and 22 are standard type switches,the operation of which switch C and relay switch 22 controllingthepassage of current into timer mechanism M. Deenergization of relayswitch 2|, upon the closing of contacts 23 in relay switch C,lie-energizes relay switches C and 22.

In the operation of this device I have found that a positive voltage of150 volts on anode a, a negative charge of 150 volts on cathode c and ongrid 9, with a plate current voltage of about 20 volts on plate 6 of theelectro-meter tube B, gives exceedingly satisfactory operating results.The current flowing to timer mechanism M may be amplified to any valuerequired to actuate the mechanism.

In place of a timer mechanism M, I may employ any other type or kind ofindicator means which may be electrically operated and which functionsto visually or audibly indicate each occurrence of negative chargeneutralization on cathode c and grid g with resultant flow of platecurrent in electro-meter tube B. All of these said indicating means areold and Well known in the art and, per se, form no part of the presentinvention except in combination with the other means and elementsthereof.

In the commercial utilization of the device of th present invention, asan exposure meter device, the photo-cell A is exposed to the lightradiation to which the photographic plate or film is to be exposed andthe time of exposure of the photographic plate or film to the radiationis limited to a determined number of negative charge neutralizationswhich by previous calibration has been found to provide in the film or'plate emulsion the desired density in the reduced metal salts producedby such film exposure. Calibration of the photo-metric device todetermine the precise amount or quantity of light radiation required toefiect the neutralization of any determined negative charge on thecathode c and grid g under controlled test conditions is neitherdifiicult nor beyond the expected skill of Q potential connected to thesaid other contact;

' actuated by said plate current to energize said relay coil to actuatesaid movable contact into closure position with the stationary contact,

thereby to impress a negative charge on the light sensitive cathode andgrid electrode electrically connected therewith to thereby terminate theflow of plate current in said 3-electrode device, means actuated by saidplate current flow to indicate the occurrence thereof, andmeans limitingthe irradiation of said photo-electric cell to radiation the quantity ofwhich is to be measured.

2. A photo-metric device comprising in combination a photo-electriccell, a thermionic device of the B-electrode type, a relay switch, and

" an electrical circuit including said cell, therone skilled in the artand does not require extended disclosure. The desired density in saidreduced metal salts may vary widely in value without essential departurefrom the invention.

It is believed apparent that the present inven tion may be widely variedwithout essential departure therefrom or from the specific embodimentthereof hereinabove given, and all such modifications and departuresfrom the same are contemplated as may fall within the scope of thefollowing claims.

What I claim is:

1. A photo-metric device comprising in com-' bination a photo-electriccell having an anode and a light sensitive cathode enclosed within aradiation permeable envelope, a 3-electrode thermionic device having athermionically active cathode, a plate electrode and a grid electrode,and a relay switch having a stationary contact,

a movable contact and an electro-magnetic coil arranged to move themovable contact into and out of closure position with the stationarycon,-

tact upon energization and de-energization of the coil, respectively,means electrically connecting the light sensitive cathode of the cell,the grid'- electrode of the thermionic device and one of the contacts ofsaid relay switch together, means mionic device and relay switch, saidcircuit including means supplying a direct current of determinedvoltage, the positive side of whichis connected to the anode electrodeof the said cell and to ground and the negative side of which isconnected to one side of the said switch with the opposite side of theswitch being electrically connected to the cathode of said cell and tothe grid electrode of said thermionic device, means providing for theflow of a plate current through said thermionic device at a determinedvoltage, means actuated by said plate current to energize theelectro-magnetic coil of said relay switch to close the contactstherein, thereby to apply the negative potential on one side of theswitch to interrupt the flow of said plate current and to charge thecell cathode negatively to the same potential on the cell anode, meanssimultaneously actuated by said plate current flow to actuate meansindicating the occurrence of said plate current flow and interruption,and means limiting the irradiation of the said cell to radiation thequantity of which is to be measured.

3. In a photo-metric device, of the exposure meter type, the combinationof a photo-electric cell, a three-electrode electro-meter tube and arelay switch, the cathode and grid electrodes of the cell and tube,respectively, being electrically connected together and to one of themovable and stationary contacts of said relay switch with the othercontact of said relay switch being electrically connected to thenegative side of a source of direct current of determined voltage, thepositive side of which is electrically connected to the anode of thesaid cell and to ground, a radiation impermeable housing enclosing thesaid photocell having an opening therein and means directing radiationto be measured therethrough onto the said photo-cell, an electricalcircuit energizing the cathode electrode of said electrometer tube, anelectrical circuit providin a desired positive voltage on the plateelectrode of said electro-meter tube and an electrical circuit includingthe actuating electro-magnetic coil of said relay switch energized bythe flow of plate current in said electro-meter tube to actuate themovable contact into closure position with the stationary contactthereby to close the circuit and to apply the negative voltage on theone contact through the other contact onto the cathode and grid elementsof the said photo-cell and electrometer tube and to open said contacts,and means also actuated by the flow of said plate current in the saidelectro-meter tube to actuate means indicating each occurrence of saidplate current flow and interruption.

4. In a photo-metric device of the exposure spaced relation within anenclosing radiation permeable envelope, a three-electrode electroxnetertube having grid, plate and cathode electrodes, and a relay switchhaving a stationary contact, a movable contact and an electro-magneticcoil to actuate the movable contact into and out of closure positionwith the stationary contact upon energization and de-energization,respectively, of the said coil, an electrical circuit means having itspositive side grounded to apply to the anode of the said photo-electriccell and to the movable contact of said relay switch, respectively, apositive and negative direct current voltage of equal and substantiallyconstant value, an electrical circuit connecting together the cathodeelectrode of the said photo-electric cell, the grid electrode of thesaid electro-meter tube .and the stationary contact of said relayswitch,

an electrical circuit including the plate electrode of saidelectro-meter tube and the energizing coil of said relay switch todirect the plate current of the said tube through the coil to energizethe coil to move the movable electrode into closure position with thestationary contact of the switch,

.means actuated by said plate current to encharge on the cathodeelectrode of said cell,

thereby to initiate plate current flow in said electro-meter tube.

5. In a photo-metric devicefor measuring the quantity of radiationirradiating an object or area, the combination of a photo-electric cell,an electro-meter tube and a relay switch, the anode of said cell beingcharged positively and grounded, the cathode and grid electrodes of saidcell and tube, respectively, being electrically connected together andto one of the contacts of the said relay switch, the opposite contact ofsaid relay switch being charged negatively to the same potential appliedpositively to the anode of the said cell, means limiting the irradiationof the said cell to radiation the quantity of which over an extendedtime interval is to be measured, an electrical circuit including theplate electrode of the said electro-meter tube and a current am-vplifier carrying the plate current flow of the said tube, an electricalcircuit including the energizing coil of the said relay switch forcarrying said amplified current; and an electrical circuit including anindicating device and means energized by said plate current fiow toenergize said circuit.

HERMANN KOTT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,818,003 Myers Aug. 11, 19311,963,342 Whitson et a1. June 19, 1934 1,973,468 Dennis Sept. 11, 19342,078,768 Meior Apr. 27, 1937 2,090,825 Anthony et al Aug. 24, 19372,309,048 Curry Jan. 19, 1943 2,386,320 Kott Oct. 9, 1945 2,434,101 CannJan. 6, 1948

